High Specific Power Polycrystalline Solar Arrays

The physical principles enabling a new class of polycrystalline thin film solar cells will be proven experimentally. The materials and device structure promise efficiency approaching that of single crystal material, even with grain sizes as small as 5 um.The new material's exceptional defect tolerance, ruggedness, and low growth temperature will enable fabrication on lightweight, flexible substrates of metal foil or polymer, giving extremely low system weight and cost. The gravimetric specific power ofsingle junction cells should approach 1.8 kW/kg, with high thermal conductivity and excellent radiation hardness. We expect to achieve 10% direct AM0 conversion efficiency in a single junction cell in Phase I, and 20% in Phase II. Analysis ofmulti-junction polycrystalline solar cell models predicts 30% direct AM0 conversion efficiency, competitive with expensive single crystal cells, and 2.7 kW/kg. The polycrystalline solar cell arrays enabled by this project promise to benefit many areas ofsolar power generation, and will supplant battery use in some applications. The bare gravimetric specific power of 1.8 - 2.7 kW/kg (AM0) can reduce launch weight or increase available payload for planes and orbiting vehicles, both civilian and military.The mechanical flexibility and defect tolerance may support 30 W of solar power per square foot terrestrially (AM1.5), deployed on foil, polymer or even fabric. Eventual compatibility with $1 per square inch manufacturing methods from the LCD industry andeven cheaper roll-to-roll manufacturing methods entails 100-fold reductions in cost per Watt compared to today's best solar cells.